Flexible electrical interconnect and method of making

ABSTRACT

A method and apparatus for making a flexible interconnect for connection between stacks of electronic components. The method includes forming a plurality of holes through a flexible insulating material, depositiong electrically conductive metal studs into the holes extending out of at least one side and preferably both sides of the flexible material, and electrically interconnecting some of the electrically conductive metal studs by interconnects supported by the flexible material. The interconnects may be supported from the outside of the flexible material or embedded therein. Dummy studs may be provided in the flexible material extending to the outside and aligned with studs extending on the other side of the insulating material which are connected to the electrical interconnects.

This application is a continuation in part of U.S. Ser. No. 07/222,487,filed 07/21/88, now U.S. Pat. No. 4,862,588, and entitled "Method ofMaking a Flexible Interconnect."

BACKGROUND OF THE INVENTION

The present invention is directed to a flexible electrical interconnectfor connection between adjacent stacks of electronic components whichmay be arranged in various configurations. Conductive metal studsembedded in the insulating material extend out of both sides of theinsulating material for coacting with adjacent stacked electroniccomponents such as electronic chips or carriers for interconnecting thestacks. Routing between the inlets and outlets of the electroniccomponents is provided by electrically interconnecting some of the studsby interconnects supported either on the outside or embedded in theflexible material. Some of the studs may be dummies which are notconnected to any of the electrical interconnects, but which are alignedwith studs that are connected to the interconnects, for providingphysical support for the active studs for making good electricalcontacts with the electronic components.

SUMMARY

The present invention is directed to a method and apparatus for making aflexible interconnect for connection between stacks of electroniccomponents which includes forming a plurality of holes through aflexible insulating material, depositing electrically conductive metalstuds into said holes extending out of at least one side of theinsulating material, and electrically connecting at least some of thestuds by interconnects supported by the flexible material.

Another object of the present invention is wherein some of theelectrically conductive metal studs may extend out of both sides of theinsulating material and in some embodiments dummy studs may be providedon the flexible insulating material on a side opposite and aligned withsome of the studs which are connected to the electrical interconnects.

Yet a further object of the present invention is the method of making aflexible interconnect by forming a plurality of holes through a flexibleinsulating material having a layer of conductive material on at leastone side, adding a resist mask layer on the conductive material anddepositing electrically conductive metal studs into at least some ofsaid holes extending out of the top and bottom of the holes andextending out of the insulating material and conductive material. Themethod includes removing the resist mask layer and applying an etch masklayer on the conductive material over the conductive material to coverdesired electrical interconnections while leaving undesired electricalinterconnections uncovered. Thereafter, the undesired electricalinterconnections are etched and the etched mask is removed.

Still a further object of the present invention is the method of makinga flexible interconnect by forming a plurality of holes through a firstflexible insulating material having a layer of conductive material on afirst side and depositing electrically conductive metal studs into theholes. The method includes applying an etch mask layer on the conductivematerial to cover desired electrical interconnections while leavingundesired electrical interconnections uncovered and etching theundesirable electrical interconnections and removing the etched mask.The method includes forming a plurality of holes through a secondflexible insulating material and bonding one side of the secondinsulating material to the conductive material. Thereafter, the methodincludes applying a resist mask on the second side of the secondinsulating material and depositing electrically conductive metal studsinto the holes of the second insulating material.

Another object of the present invention is wherein at least some of theholes in the first insulating material are aligned with the holes in thesecond insulating material. The method further includes providing dummystuds on the outside of one of the insulating materials aligned withstuds on the other side of the insulating materials.

A further object of the invention is wherein the dummy studs areprovided by applying a resist mask to the insulating material leavingthe desired locations of the dummy stud bare and depositing a dummy studinto the bare locations.

Other and further objects, features and advantages will be apparent fromthe following description of presently preferred embodiments of theinvention, given for the purpose of disclosure and taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of one form of the flexibleinterconnect and one coacting electronic component,

FIG. 2 is an elevational view, partly in section, the use of theflexible interconnect between two spaced electronic components,

FIG. 3 is a schematic perspective view of one form of the flexibleinterconnect of the present invention illustrating providing electricalinterconnects between certain of the studs in the interconnect,

FIG. 4 is an enlarged elevational view of the flexible interconnect ofthe present invention illustrating interconnection between adjacentstacks of electronic components,

FIG. 5 is an elevational view illustrating the use of the flexibleinterconnect of the present invention in another configuration ofstacked electronic components,

FIG. 6 is an enlarged fragmentary elevational view, in cross section ofthe present invention between adjacent stacks of electronic components,

FIGS. 6A, 6B, 6C and 6D are fragmentary elevational views illustratingthe method of manufacturing the flexible interconnect of FIG. 6,

FIG. 7 is an enlarged elevational view, in cross section, of anotherembodiment of the presnet invention in position between two stackedelectronic components, and

FIGS. 7A, 7B, 7C, 7D and 7E illustrate the method of manufacturing theembodiment of FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, particularly to FIGS. 1 and 2, one formof the flexible interconnect of the present invention is generallyindicated by the reference numeral 10, to serve as an interconnectionbetween at least two stacked electronic components 12 and 14, such aselectronic chips or chip carriers. The electronic components 12 and 14include a plurality of inlet or outlet pads 16 and 18, respectively,which are to be interconnected with each other or other components. Theflexible interconnect 10 includes a plurality of electrically conductivemetal studs 20 which serve the purpose of interconnecting the pads 16and 18 to desired connections as well as providing an interconnect whichwill physically coact with the components 12 and 14 to provide goodelectrical contact.

The electrically conductive metal that is used for the studs is notlimited to elemental metal, and can include alloyed mixtures as well.Preferably the studs are made of copper.

Referring now to FIGS. 3 and 4, another embodiment of the presentinvention is generally indicated by the reference numeral 10a includes aplurality of electrically conductive contact metal studs 20a having aplurality of electrical interconnects 22 for interconnecting some of theconductive studs 20a. The placement of the interconnects 22 may be asdesired depending upon the requirements of the electronic components12a, 14a and 15a. FIG. 5 illustrates another configuration for stackingcomponents 12a and 14a with a different use of the flexible connector10a.

Referring to FIG. 6, the flexible interconnect 10 is shown in anenlarged cross-sectional view being connected between electroniccomponents 12 and 14 and their respective inlet and outlet pads 16 and18, respectively, by electrically conductive metal studs 20 and suitableinterconnects such as X directed interconnects 24 and 26 and Y directedinterconnects 28, 30, 32 and 34. Preferably, the ends of the studs 20are coated with a low melting point liquid metal or fusible alloy 36such as Woods metal, Darcy alloy, gallium tin or gallium indium tin formaking a good electrical contact between the electrically conductivemetal studs 20 and the pads 16 and 18.

Referring now to FIGS. 6A-6D, the method of making the flexibleinterconnect pin of FIG. 6 is best seen. A flexible insulating material11, such as polyimide or kapton is provided with one or more layers ofan electrical conductor, such as copper, as a top layer 40 and a bottomlayer 42. By way of example only, the thickness of the insulation 11 maybe 1 to 5 mils and the thickness of the copper layers 40 and 42 may be 1to 2 mils. A resist mask is provided over the layers 40 and 42 such aslayers of resist mask 44 and 46. Any conventional resist mask may beused such as novalak or a dry film resist.

A plurality of holes 48, for example 10-25 mils in diameter, are formedthrough the structure of FIG. 6A by such means as punching, drilling,laser drilling, spark erosion, etc. As best seen in FIG. 6B the holes 48are filled by depositing an electrically conductive material therein, bysuch methods as electroplating, electroless deposition, chemical vapordeposition, laser assisted deposition, evaporation, or sputtering toprovide electrically conductive metal studs 20 which extend outwardly ofthe electrically conductive layers 40 and 42 and the insulating material11. The resist mask layers 44 and 46 are then stripped, by conventionalmeans, leaving the studs 20 and layers 40 and 42 exposed. Thereafter, anetch resist pattern, such as Shipley 1375 when copper layers are used,is placed on the layers 40 and 42 over the layers 40 and 42 and thestuds 20 to cover desired electrical connections such as the electricalinterconnections desired to form the X interconnections 24 and 26 andthe Y interconnections 28, 30, 32 and 34. The remainder of the layers 40and 42 are left uncovered for removal. Thus, referring to FIG. 6C anetch resist 52 is placed to cover the desired electricalinterconnections and the bare portions of the layers 40 and 42 areetched away by any suitable etching solution, such as sulfuric acid andhydrogen peroxide for copper layers, thereby leaving the structure ofFIG. 6D. It is to be noted that this method provides studs 20 embeddedin a flexible insulating material 11 for coacting with the pads 16 and18 of the electrical components 12 and 14 for making good contact withthe ability to be sandwiched inbetween the planar components 12 and 14and provide any suitable manner of electrical connections required.Obviously, any desired pattern of X and Y electrical interconnects maybe provided. And while the electrical interconnects can be formed bymasking the conductor layers 40 and 42 in the desired pattern andetched, the electrical interconnections may be patterned and formedalong with the studs 20 by providing a resist mask directly on theflexible insulating material 11 and depositing the interconnects thereonsuch as by electroplating.

In the embodiment of FIG. 6, the electrical interconnections 24, 26, 28,30, 32, and 34 are shown on the exterior of the flexible insulatingmaterial 11 and are therefore exposed and possibly subjected todeterioration. Referring now to FIG. 7, another embodiment of thepresent invention is shown in which the electrical interconnects areformed embedded within the flexible insulating material and thusprotected from such corrosion.

In FIG. 7, the flexible interconnect 10b is shown positioned betweenelectrical components 12b and 14b and generally includes a firstflexible insulating material layer 60 and a second flexible insulatingmaterial 62, at least one electrically conductive metal stud 20bextending through the first and second insulating materials 60 and 62for making contact between one set of contact pads 16b and 18b. Inaddition, the connection 10b may include one or more studs 64 and 66which only make connection between one of the contact pads, such as oneof pads 18b and 16b, respectively, and the electrical interconnects, butwhich are backed up by dummy studs 68 and 70, respectively, for makinggood contact between the active studs 64 and 66 and their coatingcontacts. Suitable X and Y interconnections are provided embeddedbetween the insulating material layers 60 and 62, such as Y directedinterconnections 28b, 30b and 34b and X directed interconnection 24b.

Referring now to FIGS. 7A-7E, the process of manufacturing the flexibleinterconnect 10b is best seen. A first flexible insulating material 62having a layer of electrically conductive material 70, such as copper,on a first side 72 is provided in which a plurality of holes 74 areformed. A suitable resist mask 76 is provided on the second side 78 ofthe flexible material 62, as best seen in FIG. 7B, for depositingelectrically conductive metal stud 66, the dummy stud 68, and one-halfof electrically conductive metal stud 20b.

Referring now to FIG. 7C, an etch resist mask 80 is provided over thelayer 70, to cover the desired electrical interconnections while leavingthe remainder of the layer 70 bare for forming the desired X and Ydirection interconnections. The bare material is then etched away by anydesired process, such as ion milling or wet etching, and the etched maskis removed leaving the X and Y directed electrical interconnections 28b,30b, 24b and 34b, as best seen in the lower half of FIG. 7D. Thereafter,a plurality of holes 82 are formed in a second flexible insulatingmaterial 60. The first insulating material 62 and second insulatingmaterial 60 are bonded together by bonding the side 84 of the secondinsulating material 60 to the electrically conductive layer ofinterconnects thereby embedding the X and Y directed interconnectstherebetween.

As best seen in FIG. 7E, a resist mask 86 is applied on the other side89 of the second insulating material 60 to form a pattern for depositingthe electrically dummy metal stud 70, electrically conductive metal stud64 and the remainder of electrically conductive metal stud 20b. Theresist mask is then removed forming the structure shown in FIG. 7. Thestructure of FIG. 7E may be utilized, as best seen in FIG. 7, to providea flexible electrical interconnect 10b between electrical components 12band 14b after coating the contacting surfaces of the electricallyconductive metal stud with a suitable liquid metal 90.

If desired, other means of support besides the dummy studs may be usedassure a good electrical connection between the conductive studs 64 and66, and their respective contact pads 18b and 16b.

The present invention, therefore, is well adapted to carry out theobjects and attain the ends and advantages mentioned as well as othersinherent therein. While presently preferred embodiments of the inventionhave been given for the purpose of disclosure, numerous changes in thedetails of construction and arrangement of parts will be readilyapparent to those skilled in the art and which are encompassed withinthe spirit of the invention and the scope of the appended claims.

What is claimed is:
 1. A method of making a flexible interconnect forconnection between stacks of electronic components comprising,forming aplurality of holes through a flexible insulating material, depositingelectrically conductive metal studs into said holes extending out of thetop and bottom of the insulating material, and electricallyinterconnecting at least some of the deposited studs by interconnectssupported by the flexible material.
 2. The method of claim 1 wherein atleast some of the interconnects are non-parallel.
 3. A method of makinga flexible interconnect for connection between stacks of electroniccomponents comprising,forming a plurality of holes through a flexibleinsulating material having a layer of electrically conductive materialon at least one side, adding a resist mask layer on the conductivematerial, depositing electrically conductive metal studs into at leastsome of said holes extending out of the top and bottom of the holesbeyond the insulating material and conductive material, removing theresist mask layer, applying an etch mask layer on the conductivematerial over the conductive material to cover desired electricalinterconnections while leaving undesired electrical interconnectionsuncovered, etching the undesired electrical interconnections, andremoving the etch mask.
 4. The method of claim 3 wherein at least someof the interconnects are non-parallel.
 5. A method of making a flexibleinterconnect for connection between stacks of electronic componentscomprising,forming a plurality of holes through a first flexibleinsulating material having a layer of electrically conductive materialon a first side, depositing electrically conductive metal studs intosaid holes, applying an etch mask layer on the conductive material tocover desired electrical interconnections while leaving undesiredelectrical interconnections uncovered, etching the undesired electricalinterconnections, removing the etch mask, forming a plurality of holesthrough a second flexible insulating material, bonding one side of thesecond insulating material to the electrically conductive material,applying a resist mask on the second side of the second insulatingmaterial, and depositing electrically conductive metal studs into theholes of the second insulating material.
 6. The method of claim 5wherein at least some of the holes in the first insulating material arealigned with the holes in the second insulating material.
 7. The methodof claim 5 including providing dummy studs on the outside of one of theinsulating materials aligned with studs on the other of the insulatingmaterials.
 8. The method of claim 7 wherein the dummy studs are providedby applying a resist mask to the insulating material leaving the desiredlocations of the dummy studs bare, anddepositing dummy studs into thebare locations.
 9. A method of making a flexible interconnect forconnection between stacks of electronic components comprising,forming aplurality of holes through a first flexible insulating material having alayer of electrically conductive material on a first side, depositingelectrically conductive metal studs into said holes, applying an etchmask layer on the conductive material to cover desired electricalinterconnections, wherein at least some of the interconnections arenon-parallel, while leaving undesired electrical interconnectionsuncovered, etching the undesired electrical interconnections, removingthe etch mask, forming a plurality of holes through a second flexibleinsulating material, bonding one side of the second insulating materialto the electrically conductive material, applying a resist mask on thesecond side of the second insulating material, and depositingelectrically conductive metal studs into the holes of the secondinsulating material.
 10. The method of claim 9 wherein at least some ofthe holes in the first insulating material are aligned with the holes inthe second insulating material.
 11. The method of claim 9 includingproviding dummy studs on the outside of one of the insulating materialsaligned with studs on the other of the insulating materials.
 12. Themethod of claim 11 wherein the dummy studs are provided by applying aresist mask to the insulating material leaving the desired location ofthe dummy stud bare, anddepositing a dummy stud into the bare location.13. A method of making a flexible interconnect for connection betweenstacks of electronic components comprising,forming a plurality of holesthrough a flexible insulating material having first and second sides,depositing electrically conductive metal studs into said holes extendingout of at least one side of the insulating material, electricallyinterconnecting at least some of the studs by interconnects supported bythe flexible material, and providing dummy studs on the second side ofthe flexible insulating material aligned with some of the electricallyconductive metal studs.
 14. The method of claim 13 wherein at least someof the interconnects are non-parallel.
 15. A flexible interconnect forconnection between stacks of electronic components comprising,a flexibleinsulating material having a plurality of holes, electrically conductivemetal studs deposited in said holes extending out of the top and bottomof the insulating material, and electrical interconnects between atleast some of the studs by interconnects supported by the flexiblematerial.
 16. The interconnect of claim 15 wherein at least some of theinterconnects are non-parallel.
 17. A flexible interconnect forconnection between stacks of electronic components comprising,flexibleinsulating material having first and second sides having a plurality ofholes, electrically conductive metal studs deposited in said holesextending out of at least one side of the insulating material,electrical interconnects between at least some of the electricallyconductive studs by interconnects supported by the flexible material,and dummy studs on the second side of the flexible insulating materialaligned with some of the electrically conductive studs.
 18. Theinterconnect of claim 17 wherein at least some of the interconnects arenon-parallel.